/* A simple event-driven programming library. Originally I wrote this code
 * for the Jim's event-loop (Jim is a Tcl interpreter) but later translated
 * it in form of a library for easy reuse.
 *
 * Copyright (c) 2006-2010, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <poll.h>
#include <string.h>
#include <time.h>
#include <errno.h>

#include "ae.h"
#include "zmalloc.h"
#include "config.h"

/* Include the best multiplexing layer supported by this system.
 * The following should be ordered by performances, descending. */
#ifdef HAVE_EVPORT
#include "ae_evport.c"
#else
#ifdef HAVE_EPOLL
#include "ae_epoll.c"
#else
#ifdef HAVE_KQUEUE
#include "ae_kqueue.c"
#else
#include "ae_select.c"
#endif
#endif
#endif

aeEventLoop *aeCreateEventLoop(int setsize) {
	aeEventLoop *eventLoop;
	int i;

	if ((eventLoop = zmalloc(sizeof(*eventLoop))) == NULL)
		goto err;
	eventLoop->events = zmalloc(sizeof(aeFileEvent) * setsize);
	eventLoop->fired = zmalloc(sizeof(aeFiredEvent) * setsize);
	if (eventLoop->events == NULL || eventLoop->fired == NULL)
		goto err;
	eventLoop->setsize = setsize;
	eventLoop->lastTime = time(NULL);
	eventLoop->timeEventHead = NULL;
	eventLoop->timeEventNextId = 0;
	eventLoop->stop = 0;
	eventLoop->maxfd = -1;
	eventLoop->beforesleep = NULL;
	eventLoop->aftersleep = NULL;
	if (aeApiCreate(eventLoop) == -1) /* initialize the apidata member*/
		goto err;
	/* Events with mask == AE_NONE are not set. So let's initialize the
	 * vector with it. */
	for (i = 0; i < setsize; i++)
		eventLoop->events[i].mask = AE_NONE;
	return eventLoop;

	err: if (eventLoop) {
		zfree(eventLoop->events);
		zfree(eventLoop->fired);
		zfree(eventLoop);
	}
	return NULL;
}

/* Return the current set size. */
int aeGetSetSize(aeEventLoop *eventLoop) {
	return eventLoop->setsize;
}

/* Resize the maximum set size of the event loop.
 * If the requested set size is smaller than the current set size, but
 * there is already a file descriptor in use that is >= the requested
 * set size minus one, AE_ERR is returned and the operation is not
 * performed at all.
 *
 * Otherwise AE_OK is returned and the operation is successful. */
int aeResizeSetSize(aeEventLoop *eventLoop, int setsize) {
	int i;

	if (setsize == eventLoop->setsize)
		return AE_OK;
	if (eventLoop->maxfd >= setsize)
		return AE_ERR;
	if (aeApiResize(eventLoop, setsize) == -1)
		return AE_ERR;

	eventLoop->events = zrealloc(eventLoop->events,
			sizeof(aeFileEvent) * setsize);
	eventLoop->fired = zrealloc(eventLoop->fired,
			sizeof(aeFiredEvent) * setsize);
	eventLoop->setsize = setsize;

	/* Make sure that if we created new slots, they are initialized with
	 * an AE_NONE mask. */
	for (i = eventLoop->maxfd + 1; i < setsize; i++)
		eventLoop->events[i].mask = AE_NONE;
	return AE_OK;
}

void aeDeleteEventLoop(aeEventLoop *eventLoop) {
	aeApiFree(eventLoop);
	zfree(eventLoop->events);
	zfree(eventLoop->fired);
	zfree(eventLoop);
}

void aeStop(aeEventLoop *eventLoop) {
	eventLoop->stop = 1;
}

int aeCreateFileEvent(aeEventLoop *eventLoop, int fd, int mask,
		aeFileProc *proc, void *clientData) {
	if (fd >= eventLoop->setsize) {
		errno = ERANGE;
		return AE_ERR;
	}
	aeFileEvent *fe = &eventLoop->events[fd];

	if (aeApiAddEvent(eventLoop, fd, mask) == -1)
		return AE_ERR;
	fe->mask |= mask;
	if (mask & AE_READABLE)
		fe->rfileProc = proc;
	if (mask & AE_WRITABLE)
		fe->wfileProc = proc;
	fe->clientData = clientData;
	if (fd > eventLoop->maxfd)
		eventLoop->maxfd = fd;
	return AE_OK;
}

void aeDeleteFileEvent(aeEventLoop *eventLoop, int fd, int mask) {
	if (fd >= eventLoop->setsize)
		return;
	aeFileEvent *fe = &eventLoop->events[fd];
	if (fe->mask == AE_NONE)
		return;

	/* We want to always remove AE_BARRIER if set when AE_WRITABLE
	 * is removed. */
	if (mask & AE_WRITABLE)
		mask |= AE_BARRIER;

	aeApiDelEvent(eventLoop, fd, mask);
	fe->mask = fe->mask & (~mask);
	if (fd == eventLoop->maxfd && fe->mask == AE_NONE) {
		/* Update the max fd */
		int j;

		for (j = eventLoop->maxfd - 1; j >= 0; j--)
			if (eventLoop->events[j].mask != AE_NONE)
				break;
		eventLoop->maxfd = j;
	}
}

int aeGetFileEvents(aeEventLoop *eventLoop, int fd) {
	if (fd >= eventLoop->setsize)
		return 0;
	aeFileEvent *fe = &eventLoop->events[fd];

	return fe->mask;
}

static void aeGetTime(long *seconds, long *milliseconds) {
	struct timeval tv;

	gettimeofday(&tv, NULL);
	*seconds = tv.tv_sec;
	*milliseconds = tv.tv_usec / 1000;
}

static void aeAddMillisecondsToNow(long long milliseconds, long *sec, long *ms) {
	long cur_sec, cur_ms, when_sec, when_ms;

	aeGetTime(&cur_sec, &cur_ms);
	when_sec = cur_sec + milliseconds / 1000;
	when_ms = cur_ms + milliseconds % 1000;
	if (when_ms >= 1000) {
		when_sec++;
		when_ms -= 1000;
	}
	*sec = when_sec;
	*ms = when_ms;
}

long long aeCreateTimeEvent(aeEventLoop *eventLoop, long long milliseconds,
		aeTimeProc *proc, void *clientData, aeEventFinalizerProc *finalizerProc) {
	long long id = eventLoop->timeEventNextId++;
	aeTimeEvent *te;

	te = zmalloc(sizeof(*te));
	if (te == NULL)
		return AE_ERR;
	te->id = id;
	aeAddMillisecondsToNow(milliseconds, &te->when_sec, &te->when_ms);
	te->timeProc = proc;
	te->finalizerProc = finalizerProc;
	te->clientData = clientData;
	/* new event always reside in the front of the list, so the last front will be the next of the new event */
	te->prev = NULL; /*setting the prev of the new front event means that the list is not a circular list */
	te->next = eventLoop->timeEventHead; /* make the last front as the next of the new event*/
	if (te->next)
		te->next->prev = te; /* make the new event as the prev of the last front */
	eventLoop->timeEventHead = te;
	return id;
}

int aeDeleteTimeEvent(aeEventLoop *eventLoop, long long id) {
	aeTimeEvent *te = eventLoop->timeEventHead;
	/* O(n) */
	while (te) {
		if (te->id == id) {
			te->id = AE_DELETED_EVENT_ID;
			return AE_OK;
		}
		te = te->next;
	}
	return AE_ERR; /* NO event with the specified ID found */
}

/* Search the first timer to fire.
 * This operation is useful to know how many time the select can be
 * put in sleep without to delay any event.
 * If there are no timers NULL is returned.
 *
 * Note that's O(N) since time events are unsorted.
 * Possible optimizations (not needed by Redis so far, but...):
 * 1) Insert the event in order, so that the nearest is just the head.
 *    Much better but still insertion or deletion of timers is O(N).
 * 2) Use a skiplist to have this operation as O(1) and insertion as O(log(N)).
 */
static aeTimeEvent *aeSearchNearestTimer(aeEventLoop *eventLoop) {
	aeTimeEvent *te = eventLoop->timeEventHead;
	aeTimeEvent *nearest = NULL;

	while (te) {
		if (!nearest || te->when_sec < nearest->when_sec
				|| (te->when_sec == nearest->when_sec
						&& te->when_ms < nearest->when_ms))
			nearest = te;
		te = te->next;
	}
	return nearest;
}

/* Process time events */
static int processTimeEvents(aeEventLoop *eventLoop) {
	int processed = 0;
	aeTimeEvent *te;
	long long maxId;
	time_t now = time(NULL);

	/* If the system clock is moved to the future, and then set back to the
	 * right value, time events may be delayed in a random way. Often this
	 * means that scheduled operations will not be performed soon enough.
	 *
	 * Here we try to detect system clock skews, and force all the time
	 * events to be processed ASAP when this happens: the idea is that
	 * processing events earlier is less dangerous than delaying them
	 * indefinitely, and practice suggests it is. */
	if (now < eventLoop->lastTime) {
		te = eventLoop->timeEventHead;
		while (te) {
			te->when_sec = 0;
			te = te->next;
		}
	}
	eventLoop->lastTime = now;

	te = eventLoop->timeEventHead;
	maxId = eventLoop->timeEventNextId - 1;
	while (te) {
		long now_sec, now_ms;
		long long id;

		/* Remove events scheduled for deletion. */
		if (te->id == AE_DELETED_EVENT_ID) {
			aeTimeEvent *next = te->next;
			if (te->prev)
				te->prev->next = te->next;
			else
				eventLoop->timeEventHead = te->next;
			if (te->next)
				te->next->prev = te->prev;
			if (te->finalizerProc)
				te->finalizerProc(eventLoop, te->clientData);
			zfree(te);
			te = next;
			continue;
		}

		/* Make sure we don't process time events created by time events in
		 * this iteration. Note that this check is currently useless: we always
		 * add new timers on the head, however if we change the implementation
		 * detail, this check may be useful again: we keep it here for future
		 * defense. */
		if (te->id > maxId) {
			te = te->next;
			continue;
		}
		aeGetTime(&now_sec, &now_ms);
		if (now_sec > te->when_sec
				|| (now_sec == te->when_sec && now_ms >= te->when_ms)) {
			int retval;

			id = te->id;
			retval = te->timeProc(eventLoop, id, te->clientData);
			processed++;
			if (retval != AE_NOMORE) {
				aeAddMillisecondsToNow(retval, &te->when_sec, &te->when_ms);
			} else {
				te->id = AE_DELETED_EVENT_ID;
			}
		}
		te = te->next;
	}
	return processed;
}

/* Process every pending time event, then every pending file event
 * (that may be registered by time event callbacks just processed).
 * Without special flags the function sleeps until some file event
 * fires, or when the next time event occurs (if any).
 *
 * If flags is 0, the function does nothing and returns.
 * if flags has AE_ALL_EVENTS set, all the kind of events are processed.
 * if flags has AE_FILE_EVENTS set, file events are processed.
 * if flags has AE_TIME_EVENTS set, time events are processed.
 * if flags has AE_DONT_WAIT set the function returns ASAP until all
 * the events that's possible to process without to wait are processed.
 * if flags has AE_CALL_AFTER_SLEEP set, the aftersleep callback is called.
 *
 * The function returns the number of events processed. */
int aeProcessEvents(aeEventLoop *eventLoop, int flags) {
	int processed = 0, numevents;

	/* Nothing to do? return ASAP */
	if (!(flags & AE_TIME_EVENTS) && !(flags & AE_FILE_EVENTS))
		return 0;

	/* Note that we want call select() even if there are no
	 * file events to process as long as we want to process time
	 * events, in order to sleep until the next time event is ready
	 * to fire. */
	if (eventLoop->maxfd != -1
			|| ((flags & AE_TIME_EVENTS) && !(flags & AE_DONT_WAIT))) {
		int j;
		aeTimeEvent *shortest = NULL;
		struct timeval tv, *tvp;

		if (flags & AE_TIME_EVENTS && !(flags & AE_DONT_WAIT))
			shortest = aeSearchNearestTimer(eventLoop);
		if (shortest) {
			long now_sec, now_ms;

			aeGetTime(&now_sec, &now_ms);
			tvp = &tv;

			/* How many milliseconds we need to wait for the next
			 * time event to fire? */
			long long ms = (shortest->when_sec - now_sec) * 1000
					+ shortest->when_ms - now_ms;

			if (ms > 0) {
				tvp->tv_sec = ms / 1000;
				tvp->tv_usec = (ms % 1000) * 1000;
			} else {
				tvp->tv_sec = 0;
				tvp->tv_usec = 0;
			}
		} else {
			/* If we have to check for events but need to return
			 * ASAP because of AE_DONT_WAIT we need to set the timeout
			 * to zero */
			if (flags & AE_DONT_WAIT) {
				tv.tv_sec = tv.tv_usec = 0;
				tvp = &tv;
			} else {
				/* Otherwise we can block */
				tvp = NULL; /* wait forever */
			}
		}

		/* Call the multiplexing API, will return only on timeout or when
		 * some event fires. */
		numevents = aeApiPoll(eventLoop, tvp);

		/* After sleep callback. */
		if (eventLoop->aftersleep != NULL && flags & AE_CALL_AFTER_SLEEP)
			eventLoop->aftersleep(eventLoop);

		for (j = 0; j < numevents; j++) {
			aeFileEvent *fe = &eventLoop->events[eventLoop->fired[j].fd];
			int mask = eventLoop->fired[j].mask;
			int fd = eventLoop->fired[j].fd;
			int fired = 0; /* Number of events fired for current fd. */

			/* Normally we execute the readable event first, and the writable
			 * event laster. This is useful as sometimes we may be able
			 * to serve the reply of a query immediately after processing the
			 * query.
			 *
			 * However if AE_BARRIER is set in the mask, our application is
			 * asking us to do the reverse: never fire the writable event
			 * after the readable. In such a case, we invert the calls.
			 * This is useful when, for instance, we want to do things
			 * in the beforeSleep() hook, like fsynching a file to disk,
			 * before replying to a client. */
			int invert = fe->mask & AE_BARRIER;

			/* Note the "fe->mask & mask & ..." code: maybe an already
			 * processed event removed an element that fired and we still
			 * didn't processed, so we check if the event is still valid.
			 *
			 * Fire the readable event if the call sequence is not
			 * inverted. */
			if (!invert && fe->mask & mask & AE_READABLE) {
				fe->rfileProc(eventLoop, fd, fe->clientData, mask);
				fired++;
			}

			/* Fire the writable event. */
			if (fe->mask & mask & AE_WRITABLE) {
				if (!fired || fe->wfileProc != fe->rfileProc) {
					fe->wfileProc(eventLoop, fd, fe->clientData, mask);
					fired++;
				}
			}

			/* If we have to invert the call, fire the readable event now
			 * after the writable one. */
			if (invert && fe->mask & mask & AE_READABLE) {
				if (!fired || fe->wfileProc != fe->rfileProc) {
					fe->rfileProc(eventLoop, fd, fe->clientData, mask);
					fired++;
				}
			}

			processed++;
		}
	}
	/* Check time events */
	if (flags & AE_TIME_EVENTS)
		processed += processTimeEvents(eventLoop);

	return processed; /* return the number of processed file/time events */
}

/* Wait for milliseconds until the given file descriptor becomes
 * writable/readable/exception */
int aeWait(int fd, int mask, long long milliseconds) {
	struct pollfd pfd;
	int retmask = 0, retval;

	memset(&pfd, 0, sizeof(pfd));
	pfd.fd = fd;
	if (mask & AE_READABLE)
		pfd.events |= POLLIN;
	if (mask & AE_WRITABLE)
		pfd.events |= POLLOUT;

	if ((retval = poll(&pfd, 1, milliseconds)) == 1) {
		if (pfd.revents & POLLIN)
			retmask |= AE_READABLE;
		if (pfd.revents & POLLOUT)
			retmask |= AE_WRITABLE;
		if (pfd.revents & POLLERR)
			retmask |= AE_WRITABLE;
		if (pfd.revents & POLLHUP)
			retmask |= AE_WRITABLE;
		return retmask;
	} else {
		return retval;
	}
}

void aeMain(aeEventLoop *eventLoop) {
	eventLoop->stop = 0;
	while (!eventLoop->stop) {
		if (eventLoop->beforesleep != NULL)
			eventLoop->beforesleep(eventLoop);
		aeProcessEvents(eventLoop, AE_ALL_EVENTS | AE_CALL_AFTER_SLEEP);
	}
}

char *aeGetApiName(void) {
	return aeApiName();
}

void aeSetBeforeSleepProc(aeEventLoop *eventLoop,
		aeBeforeSleepProc *beforesleep) {
	eventLoop->beforesleep = beforesleep;
}

void aeSetAfterSleepProc(aeEventLoop *eventLoop, aeBeforeSleepProc *aftersleep) {
	eventLoop->aftersleep = aftersleep;
}
